public class MyLinglist {
    public class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;
        ListNode(int val){
            this.val=val;
        }
    }
    public ListNode head;
    public ListNode last;
    //头插法
    public void addFirst(int data){
        ListNode node=new ListNode(data);
        if(head==null) {
            head = last = node;
        }else {
            node.next=head;
            head.prev=node;
            head=node;
        }

    }
    //尾插法
    public void addLast(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=last=node;
        }
        last.next=node;
        node.prev=last;
        last=last.next;
    }

    public void display(){
        ListNode cur=head;
       while(cur!=null){
           System.out.print(cur.val+" ");
           cur=cur.next;
       }
        System.out.println( );
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        int len=size();
        if(index<0||index>len){
            return;
        }
        if(index==0){
            addFirst(data);
            return;
        }
        if(index==len){
            addLast(data);
            return;
        }
        ListNode cur=findeNoOfIndex(index);
        ListNode node=new ListNode(data);
        cur.prev.next=node;
        node.prev=cur.prev;
        node.next=cur;
        cur.prev=node;
    }
    public ListNode findeNoOfIndex(int index){
        ListNode cur=head;
        while(index!=0){
            cur=cur.next;
            index--;
        }
        return cur;
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur=head;
        if(head==null){
            return false;
        }
        while(cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
       ListNode cur=head;
       while(cur!=null){
           if(cur.val==key){
               if(cur==head){
                   head=head.next;
                   if(head!=null){
                       head.prev=null;
                   }
               }else {
                   cur.prev.next=cur.next;
                   if(cur.next==null){
                       last=last.prev;
                   }else {
                       cur.next.prev=cur.prev;
                   }
               }
               return;
           }
           cur=cur.next;
       }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key) {
        ListNode cur = head;
        while (cur != null) {

            if (cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if (head != null) {
                        head.prev = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if (cur.next == null) {
                        last = last.prev;
                    } else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        if(head==null){
            return 0;
        }
        int uS=0;
         ListNode cur=head;
        while(cur!=null){
            uS++;
            cur=cur.next;
        }
        return uS;
    }

    public void clear(){
        while(head!=null){
            ListNode cur=head.next;
            head.prev=null;
            head.next=null;
            head=cur;
        }
        last=null;
    }
}
